Involvement in social relationships is associated with more health-promoting behaviors and fewer risk-taking behaviors. In turn, health behavior affects health, disability, and mortality. Previous research has considered only a couple of specific relationship types in affecting health behavior, rarely considers more than one possible mechanism linking social ties to health behavior, and has not addressed the issue of life course variation in effects. The proposed research is designed to fill these gaps and create a comprehensive assessment of social ties and health behavior over the life course by: (1) Developing profiles of health behavior trajectories over time and in relation to age, race, and gender, (2) Considering how the impact of different types of social ties on health behavior varies over the life course and by race and gender, and (3) Considering whether the most important psychosocial mechanisms linking social ties and specific health behaviors depend on age, race, or gender. Longitudinal data from a four-wave national survey covering a fifteen year time span (the Americans'Changing Lives-ACL) will be used to address these objectives. The dynamic trajectories of individual change in health behavior over time require specific analytic techniques. Growth curve analysis will be used to consider baseline levels of specific health behaviors, the rate of change in those behaviors over time, possible reciprocity between social involvement and health behavior over time, and how specific mechanisms may modify health behavior trajectories over the life course. A qualitative analysis is also proposed to elucidate the dynamic processes and symbolic meanings through which social ties affect health behavior over the life course. The proposed research is designed to identify modifiable risk and protective factors that may foster successful aging. A better understanding of the link between social involvement and health behavior over the life course will help clinicians and policy makers to identify strategic points for intervention-intervention points that are designed to target particular age groups and specific health behaviors.